Suction box with foraminous belt running thereover



June 30, 1970 E R ETAL 3,518,161

SUCTION BOX WITH FORAMINOUS BEL'I" RUNNING THEREOVER Filed March 24, 1967 INVENTORS Hmsa EAJEEG fiewsr 6:026 .D/wmsaec;

BY W

ATTOR NEYS Int. Cl. D21f'1/48" U.S. Cl .12-361 v d eclaims 1 "ABSTRACT OF THE DISCLOSURE i A suction box conveyor in which an, endless belt of woven fabric (textile or wire) passes about rolls and over a foraminous upper deck of a suction box between rolls.

Wrinkling and misalignment of the belt are avoided by driving one conveyor roll and providing it with a high friction surface such as rubber. The other conveyor roll idles and has a smooth surface. The lower run of the belt sags between the rolls. In the suction box, the hole areaisat least 20%"of the upper dcckarea and the upper edges of the holes are smoothly rounded.

The present invention relates to suction box conveyors of the type inwhich anendless foraminous belt runs over the perforated deck of a suction box and is trained about rolls.

In the past, such belts have been made of sheet rubber,

which is perforated according to a certain pattern for communicating with the perforations in the suction box deck, so that a uniformly distributed suction is obtained during the travel of the rubber belt over the suction box. However, the rubber is affected by heat and chemicals in such a way that its dimensions change. The prescribed relation between the perforations in the suction box deck and the perforations in the rubber belt is thus disturbed, with the result that dead areas can develop in which a satisfactory suction through the belt is not obtained.

To overcome this disadvantage, the perforated rubber belt can be replaced by a cloth woven of textile threads or metal wire. Such a cloth, as distinguished from a perforated rubber belt, is characterized in that it comprises a great number of fine apertures uniformly distributed across the entire cloth, so that a change in the dimension of the cloth by shrinkage or stretching has no appreciable effect on the distribution of the suction, be-

cause the relationships and the communication between the relatively large apertures in the suction box deck and the fine meshes in the woven cloth are not appreciably disturbed by such a change in dimension.

However, it is difficult to prevent such a woven cloth from developing folds or wrinkles in operation and from traveling laterally on the rolls.

The present invention solves the problem of how to use such a woven cloth without the development of wrinkles or folds and without displacement of the cloth laterally on the rolls. Y

According to the present invention, one of the rolls is a driving roll and has a surface of high friction material, preferably a soft material such as an elastomer, for example rubber or the like. The'remaining roll or rolls idle, that is, they are driven by the belt or endless member and have a smooth surface on which the cloth can slip, the tension of the belt being sufficiently low that the lower run sags slightly in a curve between the rolls.

To enable those skilled in the art to understand the invention clearly, reference is made to the disclosure herein of an embodiment by way of example. In the drawing:

FIG. 1 is a side elevational view, with parts broken 3,518,161 Patented June 30, 1970 away, of a suction box conveyor according to the present invention;

FIG. 2 is a top plan view of the conveyor of FIG. 1 with parts broken away;

FIG. 3 is an enlarged cross-sectional view of a fragment of the suction box; and

FIGS. 4 and 5 are top plan views of the structure of FIG. 3, showing two embodiments of suction box deck hole according to the present invention.

Referring now to the drawing in greater detail, there is shown a suction box 1 which is closed on all sides but has a perforated horizontal upper deck 2. The interior of suction box 1 is maintained under subatmospheric pressure by means of a vacuum line 3 that communicates with a source of vacuum such as vacuum pump (not shown).

At opposite ends of the suction box 1 are disposed rolls 4 and 5, which are supported for rotation on parallel shafts 6 and 7, respectively. The roll 4 is a drive roll, driven by power means (not shown), while the roll 5 idles. Drive roll 4 has a soft surface coat 8 of high coefiicient of friction, preferably of an elastomeric material such as rubber or the like. Idler roll 5, on the other hand, 'has a plain smooth surface having the lowest possible coefiicient of friction, substantially lower than that of the drive roll; and to this end, roll 5 may be made of polished metal or other suitable hard smooth material with low coeflicient of friction, for example ebonite.

An endless conveyor belt 9 is trained over the rolls 4 and 5, with its upper run immediately above the upper deck 2 of suction box 1. Belt 9 is an endless belt of woven cloth, and may be woven of textile threads or metal wire. If textile threads, then they may be natural or synthetic fibers, synthetic fibers being preferred, for example nylon or perlon.

As indicated above, roll 4 is driven while roll 5 idles. In fact, roll 5 is driven by conveyor belt 9. The cloth of belt 9 will skid or slip somewhat on roll 5;and as a result, longitudinal folds or wrinkles which would otherwise tend to develop in the cloth during circulation of the endless conveyor belt are avoided because the cloth on roll 5 automatically stretches or spreads parallel to the axis of the roll. Folds or wrinkles are thus avoided, which otherwise would disturb the operation in which the suction box conveyor takes part.

Moreover, it has been found that by using rolls such as 4 and 5, the tendency of the belt to become misaligned axially on one or the other of the rolls is avoided; instead, the belt is self-centering.

For satisfactory operation of the apparatus, the belt 9 should not be stretched tight between the rolls 4 and 5, but'instead its'lower run should sag slightly as shown at 12 in FIG. 1.

For most effective utilization of the uniform suction available by use of a woven cloth belt as in the present invention, the upper deck 2 of the suction box should be provided with the greatest possible number of perforations or holes 10. The holes are preferably round and their total cross-sectional area at their upper ends is preferably at least about 20% of the total deck area. In conventional suction boxes, the corresponding figure is about 10%. Good results are obtained with hole areas amounting to between 30% and 40% of the deck area.

To reduce the wear on the woven'cloth of the conveyor belt as much as possible while it passes over the suction box deck 2, the upper ends of the holes through the deck are preferably funnel shaped, that is, they have a smoothly rounded transition to the plane surface of the deck, as shown for example at 11 in FIG. 3.

FIG. 4 shows an upper plan view of the structure of FIG. 3. Alternatively, the upper ends of the holes can be in FIG. 5 touch each other and the total area within these circles is for example 78.5% of the total deck area.

Although the present invention has been disclosed and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

Having described our invention, we claim:

1. A suction conveyor, consisting of a suction box, an endless conveyor belt of foraminous cloth having its upper run disposed over the suction box and its lower run disposed under the suction box, said cloth being a woven fabric selected from the class consisting of textile threads and metal wire, a drive roll about which the ,lowenrun oftthetconveyor sagging fromone said roll to the other said roll, the suction box having a forarninous upper deck over which said upper run passes, the hole area of said deck being about 20' to about 78.5 of the total deck area. 1 T v 2. A suct ion conveyor as claimed'in claim 1,.th e holes through said deck having a smooth transition to the plane of the upper surface or said deck.

7 References Cited UNITED STATES PATENTS 2,042,198 5/1936 Swauger "162374 2,978,023 4/1961- Helland 162-351 XR 3,352,749 11/1967 Perry 1621-354 XR 3/1964 Justus et a1. 162-367 XR OTHER REFERENCES I Holt, The Paper Machine in Britt, Handbook of Pulp and Paper Technology, Reinhold Publishing Corp.

S. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner US. Cl. X.R. 162-374 

